Probing Cell Redox State and Glutathione-Modulating Factors Using a Monochlorobimane-Based Microplate Assay

Thiol compounds including predominantly glutathione (GSH) are key components of redox homeostasis, which are involved in the protection and regulation of mammalian cells. The assessment of cell redox status by means of in situ analysis of GSH in living cells is often preferable over established assays in cell lysates due to fluctuations of the GSH pool. For this purpose, we propose a microplate assay with monochlorobimane (MCB) as an available fluorescent probe for GSH, although poorly detected in the microplate format. In addition to the new procedure for improved MCB-assisted GSH detection in plate-grown cells and its verification with GSH modulators, this study provides a useful methodology for the evaluation of cell redox status probed through relative GSH content and responsiveness to both supplemented thiols and variation in oxygen pressure. The roles of extracellular interactions of thiols and natural variability of cellular glutathione on the assay performance were emphasized and discussed. The results are of broad interest in cell biology research and should be particularly useful for the characterization of pathological cells with decreased GSH status and increased oxidative status as well as redox-modulating factors.

Oxygen Dependence of Flight Performance in Ageing Drosophila melanogaster

Similar to humans, insects lose their physical and physiological capacities with age, which makes them a convenient study system for human ageing. Although insects have an efficient oxygen-transport system, we know little about how their flight capacity changes with age and environmental oxygen conditions. We measured two types of locomotor performance in ageing Drosophila melanogaster flies: the frequency of wing beats and the capacity to climb vertical surfaces. Flight performance was measured under normoxia and hypoxia. As anticipated, ageing flies showed systematic deterioration of climbing performance, and low oxygen impeded flight performance. Against predictions, flight performance did not deteriorate with age, and younger and older flies showed similar levels of tolerance to low oxygen during flight. We suggest that among different insect locomotory activities, flight performance deteriorates slowly with age, which is surprising, given that insect flight is one of the most energy-demanding activities in animals. Apparently, the superior capacity of insects to rapidly deliver oxygen to flight muscles remains little altered by ageing, but we showed that insects can become oxygen limited in habitats with a poor oxygen supply (e.g., those at high elevations) during highly oxygen-demanding activities such as flight.

Dependence of seasonal dynamics of hemorrhagic and ischemic strokes on the climate of a region: A meta-analysis

BACKGROUND

Cardiovascular events occur more often in winter than in summer; however, the dependence of strokes on various meteorological factors remains unclear.

AIMS

The purpose of this meta-analysis was to determine the dependence of the circannual dynamics of hospitalizations for hemorrhagic stroke and ischemic stroke on seasonal fluctuations in meteorological factors.

SUMMARY OF REVIEW AND CONCLUSIONS

For our meta-analysis, we selected 20 and 26 publications examining the seasonal dynamics of hemorrhagic stroke and ischemic stroke, respectively . The meta-analysis showed that hemorrhagic stroke is less likely to occur in summer than in other seasons and does not depend on a region's climate. The seasonal dynamics of ischemic stroke are not clearly expressed and are determined by the characteristics of a region's climate. In a climate without pronounced seasonal dynamics of atmospheric pressure and in wet winters, the vector of ischemic stroke incidents will not be expressed or slightly shifted toward winter. Low atmospheric pressure in summer is associated with an increased likelihood of ischemic stroke during this season compared to winter. There was also a relation between ischemic stroke risk with high relative humidity and a significant decrease in ρO₂ in summer, but there is not enough evidence regarding this association. We did not reveal dependence of the seasonal dynamics of strokes on the amplitude of annual fluctuations in air temperature.

Seasonal variations in levels of human thyroid-stimulating hormone and thyroid hormones: a meta-analysis

Seasonal dynamics in biological functions of mammals is regulated by melatonin-mediated circannual fluctuations in the secretion of thyroid-stimulating hormone (TSH) and thyroid hormones. Most anatomical and molecular structures responsive to photoperiod and melatonin secretion changes and the associated receptors are preserved in modern humans. This work aimed to determine the seasonal dynamics of TSH and thyroid hormone levels (total triiodothyronine (T3), free triiodothyronine (FT3), thyroxine (T4), free thyroxine (FT4) and to investigate the dependence of these variations on gender, age and amplitude of meteorological fluctuations. A meta-analysis of 13 panel and 7 cross-sectional studies was performed using Review Manager 5.3 (Cochrane Library). We found that circulating TSH levels were higher in winter than in other seasons, and FT4 levels were higher in autumn than in winter. T4 level had no pronounced seasonal dynamics. The level of circulating T3 was significantly higher in winter than in summer and FT3 levels were lower in summer than in autumn and spring. In addition, analysis of TSH seasonal dynamics (winter vs summer) accounting for gender differences showed pronounced increases in TSH levels during winter in women, but not in men; and also significant increases in FT4 levels during summer in men, but not in women. Seasonal dynamics of FT3 and T4 did not depend on gender. Seasonal dynamics of TSH did not change with respect to age. We also found that the extent of the seasonal dynamics of TSH is influenced by the extent of the annual dynamics of the partial density of oxygen in the air, as well as the magnitude of the annual dynamic of meteorological factors that determine it (atmospheric pressure and relative humidity).